Processing of separable fastener stringers



United Stts PROCESSING OF SEPARABLE FASTENER STRINGERS N Drawing. Application March 3, 1954, Serial No. 413,960

2 Claims. (Cl. 204-143) This invention relates to the production of separable fastener stringers and more particularly to a method for finishing the stringers.

Stringers produced from metal strip, wire, and the like by forming operations, in which the scoops are formed by stamping, punching, cutting, etc., are characterized by the presence of burrs and sharp edges and corners on the scoops. Various mechanical methods for removing the burrs and smoothening the scoops have been employed, the most usual method being the use of scratch brushes; however, the action of these brushes is not uniform due to wear of the brushes and variations in the stringers, and frequent adjusting is required. The stringers so finished are not uniform nor smooth to the touch;

they have a tendency to catch on fabric and other articles,

and they do not operate freely when coupled and un coupled.

According to the invention it is proposed to remove the burrs and sharp edges and corners from the stringers by immersing them in an electrolyte in which the metal of the scoops is anodically decomposable, connecting the scoops as anode, and passing current to the scoops. It has been found that the metal constituting the burrs and sharp edges and corners is preferentially removed during the electrolysis; this action is unlike a straight-forward dissolving action in which metal is removed evenly from all parts of the scoops. Upon removal from the solution at the conclusion of the electrolysis, the scoops of the stringers are smooth and uniform, and the stringers are exceptionally free running when coupled together.

The electrolyte is an alkaline solution of a cyanide or a pyrophosphate of a base-forming metal selected from groups Ia and Ila of the periodic table. Commonly used metals for stringers are anodically decomposable in such solutions, these metals comprising copper, high copper alloys like copper-zinc and cooper-tin and including brass, nickel, silver, bronze, aluminum, etc.; also zinc, and high zinc alloys such as the Zilloy type containing one percent copper. Metals that tend to acquire a film in the electrolyte are particularly suitable because the presence of the film may favor the preferential removal of the burrs and sharp edges and corners. Cyanide solutions are preferred, and it is desirable that the concentration of the metal cyanide in the solution shall be sufiicient to provide at least about 0.1 oz./gal. of dissolved cyanide (CN); preferably the concentration is such as to provide 3 to 19 or 20 oz./gal., and may be such as to provide up to 34 oz./gal. but usually no additional advantage is gained by concentrations much higher than about 20 oz./gal. Preferred metal cyanides are potassium cyanide, sodium cyanide, ammonium cyanide, barium cyanide, strontium cyanide, calcium cyanide; also double cyanides like potassium cuprocyanide, potassium zinc cyanide, potassium cadmicyanide, and double salts like the foregoing but in which sodium replaces potassium.

The method is carried out by immersing the stringer, either in separate or continuous lengths, joined or not to a companion stringer, in the solution, with the scoops connected as anode in a circuit comprising the solution, a cathode, and a source of direct current. A current density sufiicient to achieve the desired result Within a few minutes is employed and preferably ranges from 5 to 10 amperes per square foot (a. s. f.). Current densities as low as 0.1 a. s. f. are practical, requiring longer times; and on the other hand higher current densities, going up to a hundred or to one or two thousand a. s. f., can be used for shorter times. They very high current densities can be employed for very short periods, particularly if small areas of metal are treated at a time. In this connection, filming conditions may be advantageous. The solution temperature may range from room temperature to boiling, preferably from to F. The electrolysis is usually completed within a half hour, frequently requiring only 10 to 20 minutes. Removal of the burrs and sharp edges and corners may be controlled by regulating the concentration of dissolved cyanide in the solution, temperature, current, voltage, and time; increasing any one of these conditions ordinarily increases the rate of removal of metal, and vice versa.

When short lengths of stringers are treated, each length may be supported at its ends during immersion in the bath, one of the supports being a conductor and in contact with the endmost scoop while the other support may be in contact with only the tape portion of the stringer. Current is introduced to the scoops through the conductor support and the scoops themselves may be electrically connected in a conventional way, as by means of a metal foil, strip, rod, or wire coil. Continuous lengths of stringers, and also short lengths as well, may conveniently be treated by winding them about a metal-surfaced roll or drum and introducing current to the scoops through the metallic surface. An incident of the process is the cleaning action effected on some metals, such as the cooperand zinc-containing metals.

It is feasible, and often preferable, to carry out the invention at the time the stringers are plated. As is known, plating is usually done for decorative and/ or pro tective purposes. For zincand copper-containing metals conventional plating solutions comprising alkaline cyanide metal electroplating solutions are used, and these constitute satisfactory electrolytes for removing burrs and sharp edges and corners according to the invention. Usually the metal electrodeposited on the scoops is one of which the scoops are made, although it may be different; for example, copper or brass may be plated from cyanide solutions on scoops of zinc and high zinc' alloys, and nickel may be plated on scoops of iron or steel from a nickel plating solution. Zinc may be deposited on aluminum from a zinc containing solution. In general, the invention may be practiced during the plating of the scoops by immersing the stringer or fastener in the solution and connecting it as anode in a circuit comprising the plating solution, a cathode, and a source of direct current. Current is passed through the solution and then its direction is intermittently reversed so that the scoops become cathode for a part of the time, then anode, then cathode, etc. For example, the scoops may be anode for one minute, cathode for one minute, anode for one minute, etc.; or they may be anode for one minute, cathode for ten seconds, anode for one minute, etc. The exact times are variable and may be readily determined by the operator to suit his requirements. If desired, the procedure of alternately removing metal preferentially from the burrs and sharp edges and corners and plating the scoops may be carried out using pulsating current with the scoops anodic for at least one second at a time. As will be understood, when the scoops are anode, metal is preferentially removed from them at the burrs and the sharp edges and corners, and when they are cathode,

metal from the solution is deposited on the scoop surfaces. It has been found that metal is not deposited on the scoops in the same distribution as it is removed; in other words, the result of theprocedure is to remove the burrs, smoothen the edges and, corners, and coincidently to plate the scoops. Burr removal and smoothening is not the result .of merely depositing metal on the scoops to cover the imperfections or to build up unaffected portions of the scoops.

Conventional electroplating solutions are available for metals commonly used for making stringers. F or copper and high copper alloys, the plating solution usually comprises an alkaline solution of sodium cuprocyanide; for zinc and high zinc .alloys, the plating solution may comprise sodium zinc cyanide, sodium zincate, sodium cyanide, and sodium hydroxide. These and other conven tional solutions are described in Principles of Electroplating and Electroforming, Blurn and Hogaboom, first edition, pages 200211, 271279, 291-313, 320326, McGraw-wll, 1924.

Example A continuous length of coupled stringers, comprising a fastener chain the scoops of which were made of brass, was treated as follows: The chain, supported between upper and lower rollers, was first moved through a tank containing an alkaline cleaning solution comprising 1.5 02/ gal. of trisodium phosphate and 2 oz./ gal. of sodium cyanide, then rinsed with cold water, passed through a tank containing approximately a aqueous solution of hydrochloric acid to neutralize the alkali, rinsed in cold water, and then passed into a tank containing a solution made up from 3 oz./ gal. of copper cyanide, 4.5 oz./ gal. of sodium cyanide, and 2 oz./ gal. of sodium carbonate. In this solution, maintained at 120 F., the scoops were made anode and a direct current of 275 amperes at 12 volts was passed to them. After 5 minutes, the fastener chain was removed from the solution and introduced into a tank containing a cyanide brass plating solution made up from 4 oz./gal. of copper cyanide, 0.72 oz./ gal. of zinc cyanide, and 7.4 oz./ gal. of sodium cyanide. With the solution at 110 F. and the scoops connected as cathode, a direct current of 275 amperes at 12 volts was passed to the solution for about 5 minutes, during which time the scoops were plated with brass.

While the treatment of stringers has been described, the invention also contemplates the treatment of scoops not attached to a stringer tape since some fastener stringers are made by forming the scoops, singly or in groups, and then in a separate step applying them to a tape. Forming operations such as stamping, punching, cutting, etc. should, of course, be completed before the scoops are processed. The scoops may be treated in conventional electroplating solutions capable of producing an electro deposit on the scoops, preferably but not necessarily a deposit of a metal of which the scoops are composed. Thus, scoops of the various metals noted above may be treated as described to remove the burrs and sharp edges and corners. Additionally, scoops of aluminum or high aluminum alloys may be treated in a zinc plating solution comprising sodium zinc cyanide; scoops of tin or high tin alloys may be treated in alkaline stannate or stannous chloride solutions; scoops of steel in conventional copper, brass, zinc, cadmium, tin, or nickel electroplating solutions; scoops of nickel and high nickel alloys in nickel sulfate solutions; scoops of cobalt and high cobalt alloys in cobalt sulfate solutions; iron scoops in ferrous sulfate or chloride solutions. With the foregoing solutions alternate plating and removal of the burrs and sharp edges and corners may be carried out, as described.

More generally, formed scoops that have not yet been applied to a tape, as described above, may be treated in solutions in which the scoops are anodically decomposable, including conventional plating solutions as described, and other solutions like aqueous alkaline cyanide solutions of the kind noted, and aqueous alkaline solutions like aqueous sodium or potassium carbonate, sodium or potassium hydroxide, etc. The presence of alkali halides, such as sodium chloride, in the solution may favor the p efere tial removal of metal from the scoops. The a may be treated in a basket or plating barrel; or, particularly when groups of scoops are involved, each in the form of a longitudinal carrier comprising the re mainder of the strip from which the scoops were formed and having the scoops attached, may be treated in a manner similar to the treatment of the stringers.

In the light of the foregoing description, the following is claimed:

1. In --the method of producing separable fastener stringers, each comprising a fabric tape having spaced metal scoops mounted along one edge portion thereof, by forming said scoops from metal and mounting them on said fabric tape, said scoops being made from a metal selected from the group consisting of copper, Zinc, copper alloys, and zinc alloys and wherein the scoops are characterized by having burrs and sharp edges and corners such that they are difficult to couple and uncouple the improved steps of finishing the scoops which comprise connecting the spaced scoops of a stringer to an electrical conductor, then immersing said stringer including the fabric thereof in an alkaline cyanide metal electroplating solution the metal of said solution being selected from the class consisting of copper, zinc, copper alloys and zinc alloys, the concentration of dissolved cyanide (CN) being about 0.1 to about 20 oz./gal., connecting said scoops as anode in a circuit comprising said plating solution, a cathode, and a source of current, passing current through the solution for a substantial period of time to remove at least a portion of the metal from the scoops preferentially at the burrs and the sharp edges and corners thereof to produce a stringer having scoops having substantially reduced burrs and sharp edges and corners and being substantially smooth to the touch and being freely running when coupled and uncoupled with a similarly treated companion stringer, then reversing the direction of current to plate metal from the solution on the surfaces of the scoops, and continuing to intermittently change the direction of current to produce a finished stringer having plated scoops.

2. A method according to claim 1 wherein the current employed is in the range of 5-l0 amperes per square foot and the temperature of the solutions is maintained at about to about F.

References tilted in the file of this patent UNITED STATES PATENTS 1,787,139 Cain ec. 30, 1930 2,451,341 Iernstedt Oct. 12, 1948 2,591,042 Berrnan et al Apr. 1, 1952 2,715,095 Cohn Aug. 9, 1955 FOREIGN PATERTS 27,099 Great Britain of 1906 655,514 Great Britain July 25, 1951 OTHER REFERERCES Proceedings of The American Etectroplaters Society, June 1946, pages 53 and 54 of article by Faust. 

1. IN THE METHOD OF PRODUCING SEPARABLE FASTENER STRINGERS, EACH COMPRISING A FABRIC TAPE HAVING SPACED METAL SCOOPS MOUNTED ALONG ONE EDGE PORTION THEREOF, BY FORMING SAID SCOOPS FROM METAL AND MOUNTING THEM ON SAID FABRIC TAPE, SAID SCOOPS BEING MADE FROM A METAL SELECTED FROM THE GROUP CONSISTING OF COPPER, ZINC, COPPER ALLOYS, AND ZINC ALLOYS AND WHEREIN THE SCOOPS ARE CHARACTERIZED BY HAVING BURRS AND SHARP EDGES AND CORNERS SUCH THAT THEY ARE DIFFICULT TO COUPLE AND UNCOUPLE THE IMPROVED STEPS OF FINISHING THE SCOOPS WHICH COMPRISE CONNECTING THE SPACED SCOOPS OF A STRINGER TO AN ELECTRICAL CONDUCTOR, THEN IMMERSING SAID STRINGER INCLUDING THE FABRIC THEREOF IN AN ALKALINE CYANIDE METAL ELECTROPLATING SOLUTION THE METAL OF SAID SOLUTION BEING SELECTED FROM THE CLASS CONSISTING OF COPPER, ZINC, COPPER ALLOYS AND ZINC ALLOYS, THE CONCENTRATION OF DISSOLVED CYANIDE (CN) BEING ABOUT 0.1 TO ABOUT 20 OZ./GAL., CONNECTING SAID SCOOPS AS ANODE IN A CIRCUIT COMPRISING SAID PLATING SOLUTION, A CATHODE, AND A SOURCE OF CURRENT, PASSING CURRENT THROUGH THE SOLUTION FOR A SUBSTANTIAL PERIOD OF TIME TO REMOVE AT LEAST A PORTION OF THE METAL FROM THE SCOOPS PREFERENTIALLY AT THE BURRS AND THE SHARP EDGES AND CORNERS THEREOF TO PRODUCE A STRINGER HAVING SCOOPS HAVING SUBSTANTIALLY REDUCED BURRS AND SHARP EDGES AND CORNERS AND BEING SUBSTANTIALLY SMOOTH TO THE TOUCH AND BEING FREELY RUNNING WHEN COUPLED AND UNCOUPLED WITH A SIMILARLY TREATED COMPANION STRINGER, THEN REVERSING THE DIRECTION OF CURRENT TO PLATE METAL FROM THE SOLUTION ON THE SURFACES OF THE SCOOPS, AND CONTINUING TO INTERMITTENTLY CHANGE THE DIRECTION OF CURRENT TO PRODUCE A FINSIHED STRINGER HAVING PLATED SCOOPS. 